Abstract: With the increasing power of wind turbines and the application of new composite materials, the flexibility and geometrically nonlinear deformation of blades have become important parts in wind turbine design. As a consequence, the structural analysis becomes more complex and thus their aeroelasticity accordingly. However, traditional blade analysis methods in the wind energy industry cannot predict the aeroelastic behavior of these modern complicated blades, which leads to an inaccurate estimation of the turbine performance. Based on the flexible multi-body dynamics, a new two-way fluid-structure coupling analysis method is established in the present study. The model retains the traditional actuator line model and considers the influence of aeroelasticity on the performance of the rotor. This work verifies the accuracy of the model through a 5 MW baseline wind turbine, investigates the transient structural response of the blade, and analyzes the influence of blade deformation on the rotor power and wake. The results show that the flexibility of blades cannot be ignored in the aeroelastic design of wind turbines. Moreover, the model can accurately capture the wake structure of the rotor, including the blade tip and blade root vortices, which is more suitable for the aeroelastic and wake analysis of modern megawatt-level composite wind turbines.